Let's also make one thing clear.

Forum community /= Ingame community

I'll say that the FFXIV community is good, better than most mmorpg's. But calling it the best one? No, not really. Too much of people easily raging/quitting over minor stuff. Or people not wanting to listen to good advice. And also the mentality of wanting to help people seems to have mostly faded. (Seriously, it doesn't take long to help someone clear a storymode primal fight...)

FFXI had the best community in my eyes. But that was also because the game caused such mentality to exist. iRO had a good ingame community as well.